DE102006008300A1 - Highly efficient phosphor from oxynitridosilicates with cation, used in white light emitting diodes - Google Patents

Abstract

In a highly-efficient phosphor from the class of oxynitridosilicates with a cation, the oxynitridosilicate completely or predominantly comprises a phase, which corresponds to neither the pure Sr-SiON nor the pure Ba-SiON, where the dominant wavelength of the mixer-SiONs at given doped content of at least 6 nm, preferably at least 8 nm, compared to the dominant wavelength of the pure Sr-SiON with same doping content, is shifted to longer wavelengths. A highly-efficient phosphor from the class of oxynitridosilicates with a cation M 2+> has a basic formula M (1-c)Si 2O 2N 2:D c, where the oxynitridosilicate completely or predominantly comprises a phase, which corresponds to neither the pure Sr-SiON the pure Ba-SiON, where the dominant wavelength of the mixer-SiONs at a given doped content of at least 6 nm, preferably at least 8 nm, compared to the dominant wavelength of the pure strontium-sion with same doping content, is shifted to longer wavelengths. M 2+> = Sr 2+> and Ba 2+>; D = a bivalent doping with at least europium; M = Sr (1-x)Ba x; and x = 0.3-0.7, preferably 0.45-0.55. Independent claims are also included for the following: (1) a light source with primary radiation that is totally or partly converted into long light-wave radiation by the phosphor; and (2) the production of a mixer-SiON, comprising intensively mixing carbonate of strontium and of barium together with silicon dioxide and a fluxing agent as well as one europium precursor to synthesis orthosilicate and mixing orthosilicate with silicon nitride, where the mixture is subsequently glowed in mild reducing atmosphere.

Description

technical area

The The invention is based on an oxynitride phosphor and relates Furthermore a light source, in particular LED, with such a phosphor. The phosphor belongs the class of the sione. The invention further relates to a production method for one such phosphor.

was standing of the technique

WO-A 2005/030905 describes a phosphor and a preparation method for a mixed Sion, which is an oxinitridosilicate of the formula MSi ₂ O ₂ N ₂ (M = Ca, Sr, Ba), which is activated with divalent Eu, under evtl Further addition of Mn as coactivator, wherein the phosphor predominantly or alone, that is to say more than 50% of the phosphor, preferably more than 85% of the phosphor, consists of an HT phase. This HT modification is distinguished from the NT phase in that it can be excited in a broadband manner, namely over a wide range from 50 to 480 nm, in particular from 150 to 480 nm, particularly preferably from 250 to 470 nm, to an extremely high level Stability against external influences, so at 150 ° C in air shows no measurable degradation, and that it shows an extremely good color stability in changing conditions. Other pluses are its low absorption in the red, which is particularly advantageous in phosphor mixtures. A predominance of the HT modification is evident inter alia from the fact that the characteristic peak of the NT modification in the XRD spectrum at about 28.2 ° an intensity of less than 1: 1, preferably less than 1: 2, compared to the peak with highest intensity from the triad of reflections of HT modification, which are in the XRD spectrum at 25 to 27 °, has.

The WO-A 2004/039915 discloses a phosphor and a light source with a crystal structure in the orthorhombic system. The sion has the stoichiometry MSi2O2N2: Eu. It is, for example, a mixed sion with M = (Sr, Ba), wherein preferably the molar ratio Sr: Ba is at 6: 4 to 9: 1.

presentation the invention

It Object of the present invention, a phosphor according to the preamble of claim 1, the efficiency of which possible is high. Another task is to create a light source with this phosphor and a method of making this effective phosphor specify.

These Tasks are characterized by the characterizing features of the claim 1, 13 and 17 solved. Especially advantageous embodiments can be found in the dependent claims.

So far There is no high efficiency yellow emitting phosphor which at the same time insensitive to external influences and also by Blue or UV radiation, in particular by primary radiation of LEDs, good excitable. As the phosphor according to the invention by both Blue as well as by UV radiation, is well excitable, it is suitable also for other light source, where an excitation in this spectral range possible is, such as Hg low-pressure fluorescent lamps, as a shift pigment in conjunction with blue-green electroluminescent phosphors or related to Lamps, the molecular radiation of metal iodides such as indium iodide use.

The starting point of the new invention is the surprising finding that there is another phase of the Sion phosphor which occurs only in the mixture between Sr-Ba but not in the pure Sr-Sion and Ba-Sion. It behaves differently and shows different XRD reflexes than the previously known Sione. A distinguishing feature of this new phase is that the dominant wavelength is not, as would be expected, between that of the Sr sion and that of the Ba sion with respect to a given Eu doping level, but surprisingly much longer wavelength than the dominant wavelength of the corresponding Sr sion is shifted by at least 6 nm to longer wavelengths. Typical is a shift of 8 to 10 nm. The phase can be represented as M _1-c Si 2 O 2 N 2: Eu _c with M = Sr _1-x Ba _x .

Prefers is the mixed sion so chosen that 0.42 ≤ x ≤ 0.70, in particular 0.45 ≤ x ≤ 0.55.

there are the best results with a relatively high content of the dopant achieved. As a rule, the activating dopant is alone or far predominantly Europium. The proportion c of the Eu should be between 0.1 and 20 mol% of M, preferably 5 to 12 mol%.

Of the new phosphor is characterized by X-ray diffraction pattern (XRD spectrum) a completely different reflex pattern than the well-known Sione. It is not excluded that also other metals in smaller quantities one at least ternary Connection for construct the host lattice of the mixed sion, which apart from Sr and Ba also other bivalent Metal ions, in particular Ca, Mg, Zn and Mn contained. These show a similar Structure like the new mixed-sion, due to the similar reflexes of the X-ray diffraction pattern s is recognizable.

Is striking, that the highest intensity reflex of the new phosphor is a double peak, which is opposite to the most intense XRD reflex of Sr-Sion, which is at about 31.6 ° when excited by Cu Kα, at shorter angles is postponed. It shows up in high resolution Double peak with maxima at about 29.8 and 31.3 °. It is also noticeable, inter alia, that a group of three reflections in the X-ray diffraction pattern between 52 ° and 58 ° occurs, which is not present in normal sions.

One possible cause of the occurrence of the new phase, at a suitable production process is the careful choice of the mean ion size of the ion M ^2+. As soon as the average ionic radius falls below a critical size, a blue band emitted from the pure Ba-sion phase discussed above disappears almost completely. This can preferably be achieved by targeted modification of the Ba-Sr ratio.

For example is formed at a mean ionic radius of the ion M2 + of at most 0.13 nm this completely new phase that makes it so binary apparently only in the mixed sion of Sr and Ba. She has another one Emission spectrum in which the blue band plays no role. In this phase depends the position of the emission band is very much dependent on the doping content. With increasing content of Eu, the emission shifts markedly long-wave.

The new phase leaves For example, according to the following Prepare a regulation: The carbonates of the metals are used M, especially the carbonates of Sr and Ba. They are made with SiO2, Si3N4, Eu2O3 mixed. proven has become the use of a halide flux such as especially SrF2, BaF2, SrCl2 or NH4F. These batch mixtures react under heating to 1450-1650 ° C in light reducing atmosphere, which preferably at least one of the components such as Ar, N2, H2 or Forming gas (N2 / H2) contains. Crucial here is a sufficiently good mix of Sr and Ba precursors.

A other manufacturing route that is less sensitive with regard to the mixture of Sr and Ba precursors is over Orthosilicates.

The XRD lines of the new phase can be indicated orthorhombisch. The new phase, however, can be assign no known phase. An examination of the cell volume however, this assumption provides surprising results. at an adaptation of the lattice parameters to the measured diffractograms assuming the orthorhombic unit cell shows, strangely enough, the cell volume with increasing Ba content first decreases significantly, though with Ba2 + a larger cation versus the smaller one Sr2 + is exchanged. In the range of 30 to 58 mol% Ba changes then the apparent cell volume hardly, then it rises again. This leaves the easiest way to explain this that the chosen one Elementary cell just not the physically relevant unit cell equivalent. Independently however, it is clear that if suitably manufactured, it will be three distinct mutually distinguishable regions in the mixed sion (Sr, Ba) -Sion gives. A first Range is the well-known Sr-dominated mixed sion (about 70 to 100% Sr content), a second region is the well-known Ba-dominated mixed sion (approx 70 to 100 Ba content). The new phase of a real mixed-sion occurs when suitably chosen Production conditions in the range 30 to 70% Sr content, balance Ba, on. very good the new phase is in the range of 30 to 58 mol% Ba, especially at 45 to 55 mol% Ba.

The new phase is also preserved when you use small amounts of others adds divalent ions. When Ca is added, the possible Ba content shifts to higher levels.

Of the The finding of a new phase is supported by the fact that pure Sr-Sion emits green and pure Ba-Sion emits even more shortwave, namely teal. On the other hand The new mixed sion emits yellow, ie longer-wave than pure Sr Sion.

Typically, for white LED applications, an Eu content of 5 to 20% is chosen so that the phosphor's dominant wavelength in the yellow spectral range is at least 569 nm. A value of c = 0.1 is typical, ie an Eu proportion of 10% of M. This corresponds to a dominant wavelength of about 573 nm.

As a result, the known yellow garnet phosphor YAG: Ce can be replaced by a novel oxinitride phosphor Sr1-xBaxSi2O2N2: Eu with 0.7 ≥ x ≥ 0.3, for yellow emission. This phosphor has in the composition with x by 0.5 and 10% Eu doping in about the same dominance wavelength as alternative Gelbleuchtstoffe (garnets, orthosilicates). The phosphor whose emission band is surprisingly not between blue-green (BaSi2O2N2: Eu) and yellow-green (SrSi2O2N2: Eu), but is long-wave yellow in relation to both compounds, has two important advantages over the prior art, as he by the use of garnet phosphors is characterized (orthosilicates are even more inefficient than YAG: Ce):
First, the visual benefit, depending on the compound 10-15% higher than comparable garnet phosphors. And secondly, the conversion efficiency loss at 150 ° C decreases from at least 20% in the case of garnet phosphors to about 7%.

In order to is the potential efficiency advantage of a white LED (color location x / y = 0.33 / 0.33) based on the new phosphor and a 455 nm primary LED 150 ° C approx. + 20% compared to a YAG: Ce-based solution (x / y = 0.32 / 0.33). Of the Efficiency advantage increased at shorter Excitation wavelengths, as the conversion efficiency to YAG increases.

Amazingly, corresponds to the X-ray diffraction pattern and thus the structure of SrBa-SiON neither the Ba-SiON nor that of Sr-SiON. With the SrBa SiON significantly fewer lines in the x-ray diffraction observed as the Sr-SiON, which proves that it is a higher symmetric new phase.

conditioned due to ever increasing power of the LEDs as well as ever broader Fields of application will in the future be LED temperatures (junction temperatures) from above 150 ° C reached. At these high temperatures is also the most efficient yellow garnet phosphors such as YAG: Ce already a noticeable temperature quenching of Luminescence on (thermal quenching). You lose at least 20% their conversion efficiency in relation to the efficiency at room temperature. So far, the LED temperature has been through complex cooling measures, that from the market in many cases can not be tolerated and in many applications for reasons of space not possible are, as possible kept low temperatures. The new Misch-Sion offers here a superior one Solution.

It but also for other light sources are used, for example ordinary Lamps such as high pressure discharge lamps and fluorescent lamps.

The new mixed phase can also be used with other phases of sions, in particular Sr-Sion, to be mixed.

Especially surprising is that the new phase will be even more efficient than garnet phosphors can and thus even YAG: Ce can replace.

Around the new phase as possible To obtain pure, a suitable manufacturing process must be used. It is less recommended the synthesis of nitrides, as usually previously used, because nitrides are not available especially fine-grained are. To add an intimate mixture of the Sr and Ba precursors However, it is preferably fine-grained Sr and Ba precursors to use a maximum d50 (measured with Sedigraph) of at the most 5 μm, preferably even at most 3 microns, own. Good results come with precursors scores between 1 and 2 μm as d50.

At the easiest ones the new Sion over produce an orthosilicate route, but also a suitably modified Synthesis from carbonates is possible in particular using a relatively high proportion of dopants. Especially a high Eu content of at least 1%, preferably at least 5%, seems to favor the training of the new phase. In particular, the radiation stability of the new mixed sion is higher than in the previously known phases.

Particularly suitable is the new phosphor for use with white LEDs. An x-value for Ba of 30 to 70% can be used, while using a relatively high Eu content of at least 5%. It is very well suited for the excitation in the spectral range at 440 to 465 nm, which is particularly good at excitation by a peak wavelength of the LED at 440 to 450 nm. The dominant wavelength of the phosphor can be very well in a range between 569 and 578 nm put.

short Description of the drawings

in the The invention is based on several embodiments be explained in more detail. The figures show:

1 Diffractograms of different sions of the type MSi2O2N2: Eu;

2 the cell volume as a function of the Sr content;

3 . 4 in each case a detailed section of the X-ray diffractogram of various mixed ions;

5 the comparison of the emission of a known orthosilicate with the novel mixed sion;

6 the comparison of the emission of a known garnet with the novel mixed sion;

7 the efficiency of different phosphors as a function of ambient temperature;

8th the shift of the emission band (maximum) as a function of the Sr content;

9 a comparison of the emission spectra of a mixture invention with the pure Sione;

10 Emission spectra of further mixed sions;

11 an emission spectrum of a white LED with the participation of the novel phosphor.

12 a white LED;

13 a light source based on LEDs;

14 a light source based on a low pressure lamp.

preferred embodiment the invention

1 shows X-ray powder diffractograms of Eu-doped phosphors of the Ba0.95Si2N2O2 type: Eu0.05 (top), Sr0.9Si2N2O2: Eu0.1 (bottom) and Ba0.45Sr0.45Si2N2O2: Eu0.1 (center). It can be seen that the diffractograms clearly differ from each other. The diffractogram of Sr-Sion still contains the peaks of the diffractogram of Ba-Sion (slightly shifted due to smaller lattice parameters) but is more line-rich. This indicates a structure with lower symmetry. The reflection pattern of BaSr-Sion is distinctly different from that of the two boundary phases, ie there is no mixture of the two pure boundary phases.

2 Figure 3 shows the cell volume of the phosphor as a function of Sr content in the Sr-Ba system prepared via the carbonate route. An orthorhombic unit cell is assumed. Matching the lattice parameters to the measured diffractograms assuming an orthorhombic unit cell provides unusual results. It can be seen that the apparent "cell volume" surprisingly initially decreases significantly with increasing Ba content, although with Ba ²⁺ a larger cation is increasingly incorporated. In the range of 20% to 50% Sr, the apparent "cell volume" barely changes; then it rises again. This indicates that the selected cell does not correspond to the physically real unit cell. Nevertheless, it can be concluded from the peak shift that there are three distinctly different regions: 0-10% Sr, about 20-65% Sr, and 70% -100% Sr. Transition ranges are 10 to 20% Sr and 65 to 70% Sr.

3 shows a detail from the X-ray diffraction pattern for different mixed Sione in the range 32 to 36 ° for the angle 2 Θ. An overview of six samples with different Sr / Ba ratio is shown. The Ba content increases from bottom to top, from diffractogram to diffractogram, each by 20%. (The Eu share of 2% was evenly distributed to both "squares".) The spectra are shown in the following figures with respect to the angular range spread in order to discuss the differences better. The labeled reflex groups remain at nearly the same position within a structure with increasing Sr content. The labeled reflex groups remain at nearly the same position within a structure with increasing Sr content. However, there is a twofold increase in position and intensity in the phase transitions from Ba-SiON to SrBa-SiON and from SrBa-SiON to Sr-SiON. Typically, from about 35% Sr, a new, yellow-emitting SrBa-SiON phase is obtained, which becomes more and more distorted with increasing Sr content above 60% Sr and continuously changes into the Sr-SiON phase. The exact values depend on the Eu doping and on any additionally incorporated cations (eg Ca, Zn, Mg, Yb).

4 shows the highest intensity peak of Sr-Ba mixed sion in its position relative to the highest intensity peak of Sr sion and Ba sion. The highest intensity peak of the mixed sion is about 2 Θ = 31.2 °. It is actually a double peak, which coincides here due to poor resolution. By contrast, the peak of Sr and Ba sion with the highest intensity is located at much higher wavelengths of almost 2 Θ = 32 °.

5 shows the comparison of the emission band of a mixed-ion type phosphor according to the invention with a yellow orthosilicate of the prior art. With the new SrBa-SiON: Eu practically the same spectral distribution can be achieved as with orthosilicates.

6 shows the comparison of the emission band of a mixed-ion type phosphor according to the invention with a yellow garnet phosphor of the prior art. The emission band is much narrower at nearly the same dominant wavelength. The visual benefit of the emission radiation is therefore significantly higher, typically around 10%.

7 shows the comparison of the efficiency of the invention mixed-ion type phosphor with the prior art (YAG: Ce and (Sr, Ba) -Orthosilikat: Eu) as a function of ambient temperature. The new phosphor is significantly more temperature stable than the prior art.

8th shows the comparison of the emission of different mixed ions with UV excitation at 400 nm. For x to 30%, a second band is still visible in the blue. High efficiencies are also achieved with blue excitation, typically at 440 to 460 nm, only in compositions in which the blue emission observed at 400 nm excitation is largely suppressed. Preferably, a fraction f = 1-x of (1-x) ≥ 40%, more preferably (1-x) ≥ 45%, wherein at f each of the Eu content is added to the Sr content, so f = f (Sr, Eu).

8th shows the shift of the emission bands of Ba _x Sr _1-x Si ₂ O ₂ N ₂ : Eu (2%) phosphors. The blue emission band disappears almost completely at 1-x> 30%. Between 1-x = 30% and 1-x = 60%, the position of the long-wave emission band remains almost constant. The dashed line indicates the phase transition region. For higher Sr concentrations, a shift of the wavelength towards green Sr-SiON: Eu emission can be achieved without decreasing the efficiency. The emission wavelength can therefore be adapted well to the respective requirements. For short-wavelength blue primary LEDs (eg 440-450 nm), for example, a slightly shorter wavelength phosphor has to be used for white generation than in the case of a longer-wavelength blue primary LED (460 nm peak excitation).

9 : The emission spectrum of the novel mixed Sione is significantly broader than that of Sr-Sion. The mixed sion alone is well suited for color temperatures of 4000 to 6500 K, preferably 4500 to 6000 K.

It let yourself but also good with Sr-Sion or other sions or nitrides such as (Sr, Ca) Si5N8: Eu or CaAlSiN3: Eu combine. Especially at Use together with Sr-Sion will thus reduce the total emission depending on the proportion between green (pure Sr-SiON: Eu) and yellow (novel mixed-sion SrBa-SiON: Eu) moved continuously. This can be changed in particular the color. This combination is suitable in combination with a red phosphor especially good for warm white LED with color temperature from 2800 to 3800 K, with a high Ra of at least 85 can be achieved.

To adapt the emission behavior, a ternary mixed sion based on the Sr-Ba-sion can also be used. In particular, Ca is suitable in small quantities. Alternatively, another bivalent ion with a similar low ionic radius as Ca may be used. A similar low ionic radius is achieved in particular with addition of Zn, Mg, Mn and Yb instead of or together with Ca. The proportions should be so small that the typical structure of the mixed sion is maintained, and in particular the double peak at 2 Θ = 31.2 ° (relative to Cu K α) clearly emerges.

The preparation of the novel phosphor according to the invention can take place via the orthosilicate route. First, carbonates of Sr and Ba together with SiO2 and a flux such as SrF2 or the like. and an Eu precursor intensively mixed and homogenized. Subsequently, an orthosilicate is synthesized by annealing the mixture in an Al ₂ O ₃ crucible under forming gas. this takes place gradually over several hours up to a temperature of about 1100 to 1400 ° C. The orthosilicate is then mixed with Si3N4 and homogenized, and this mixture is then annealed in a slightly reducing atmosphere (Ar or N2 or H2 or mixtures) in the tungsten crucible. The temperature is gradually increased over several hours up to 1400 to 1600 ° C.

Tab. 1

The preparation of the novel phosphor according to the invention is also possible via the carbonate route. Table 1 shows the preparation of the mixed sion Sr _0.45 Ba _0.45 Eu _0.1 Si ₂ O ₂ N ₂ . In this case, a mean particle size of approximately 1.6 μm is used for the precursors SrCO3 and BaCO3.

The preparation is carried out in such a way that initially the starting materials SrCO ₃ BaCO ₃ , (or BaSrCO _3, ), SrF 2, Si ₃ N ₄ and SiO ₂ are mixed thoroughly with each other and the mixture then in the oven at 1500 to 1600 ° C under slightly reducing atmosphere is annealed for 8 hours. In this case, a substantially stoichiometric approach is taken, see Tab. 1.

Of course, the Sion shown does not have to have an exact stoichiometry MSi2O2N2, but only its basic formula. Deviations are also allowed. Such a phosphor can be described as a primarily yellow-emitting oxynitride phosphor having a stoichiometry:
MSi ₂ O _{2 + δ} N _{2- (2/3) δ} , where M = (Sr ₁ -x Ba _x ) _1-c Eu _c

For δ applies
1 ≥ δ ≥ -1, preferably 0.35 ≥ δ ≥ -0.35.

A Analysis of the O- and N-contents gives, for example, 14.4% by weight of O. and 10.0 wt% N, which is nominally equal to a δ of +0.29. Indeed can not be ruled out, that one Deviation of the measured values from the theory by still in small Dimensions available Foreign phases such as in particular SiO2 and Si2ON2 is affected, so that in the concrete case the true value of δ is about 0.25 to 0.35. Typically you can also impurities less than 200 ppm due to contamination of the Starting materials are formed. But these small impurities change the properties of the phosphor are not fundamental.

A particularly high-quality white LED with a high Ra can be achieved if the yellow mixed ion according to the invention is used together with other phosphors. These should be especially special fill the spectrum in the red spectral range. Suitable candidates here are in particular red nitrides and red sulfides as known per se. Examples are CaAlSiN3: Eu, and (Sr, Ca, Zn) S: Eu or also (Ba, Sr, Ca) 2Si5N8: Eu.

In Tab. 2 is the dominant wavelength of pure Sr-sion as Function of the europium doping content shown. This serves as a guide for the achievable displacement by means of the mixed sion, which at least 6 nm, often at least 8 nm, towards longer ones wavelength lies.

Finally shows 11 the spectrum of a white LED with a color temperature of 6000 K based on an emitting in the blue with peak wavelength 460 nm LED and a yellow emitting phosphor according to the invention. Both mix together to white.

In Table 3 is finally a comparison of different data for essential phosphors shown.

The construction of a light source for white light is in 12 shown explicitly. The light source is a semiconductor device with a chip 1 of the type InGaN with a peak emission wavelength in the UV of, for example, 440 nm, which forms an opaque base housing 8th in the region of a recess 9 is embedded. The chip 1 is over a bonding wire 14 with a first connection 3 and directly with a second electrical connection 2 connected. The recess 9 is with a potting compound 5 filled, containing as main components an epoxy casting resin (80 to 90 wt .-%) and phosphor pigments 6 (less than 20 wt .-%). Part of the blue primary radiation is absorbed by the yellow-emitting phosphor Sr 0.45 Ba 0.45 Siu 0.1 Si 2 O 2 N 2, so that total white light is emitted. The recess has a wall 17 acting as a reflector for the primary and secondary radiation from the chip 1 or the pigments 6 serves.

In a further embodiment according to 13 again a mixed ion as explained above and a red-emitting nitridosilicate is used as the phosphor pigment, in particular a red-emitting nitridosilicate of the type CaSrSi5N8: Eu. However, these are on the walls 9 an outer housing containing a plurality of LED luminescence conversion LED type.

14 shows a low-pressure discharge lamp 20 with a mercury-free gas filling 21 (Schematically), which contains an indium compound and a buffer gas analogous to WO 02/10374, wherein a layer 22 SrBaSi ₂ O ₂ N ₂ : Eu inside the piston 23 is appropriate. The particular advantage of this arrangement is that this mixed ion is well adapted to indium radiation because it has substantial levels in both the UV and blue spectral regions, both of which are equally well absorbed by this mixed ion, giving it makes superior in this use against the previously known phosphors. These known phosphors absorb appreciably either only the UV radiation or the blue radiation of the indium, so that the indium lamp according to the invention shows a significantly higher efficiency. This statement also applies to a high-pressure indium lamp as such US 4,810,938 known.

Tab. 2

Claims (13)

Highly efficient phosphor of the class of the oxinitridosilicates with a cation M2 + and the basic formula M _(1-c) Si ₂ O ₂ N ₂ : D _c , where M2 + as component Sr2 + and Ba2 + simultaneously, and wherein D is a bivalent doping with at least europium is characterized in that for M = Sr _(1-x), Ba _{x is used} with 0.3 ≤ x ≤ 0.7, wherein the oxynitridosilicate consists entirely or predominantly of a phase which is neither that of pure Sr-Sion nor which corresponds to pure Ba-Sion, wherein the dominant wavelength of the mixed sion at a given doping content by at least 6 nm, preferably by at least 8 nm, compared to the dominant wavelength of the pure Sr sion with the same doping content is shifted towards longer wavelengths. Phosphor according to claim 1, characterized in that that x is chosen is 0.42 ≤ x ≤ 0.70. Phosphor according to claim 1, characterized in that that the structure of the phosphor has a higher symmetry than that of the having pure Sr sions. Phosphor according to claim 1, characterized in that the proportion c of the Eu is between 0.1 and 20 mol% of M, preferably 5 to 12 mol%. Phosphor according to claim 1, characterized in that that 0.45 ≤ x ≤ 0.55. Phosphor according to claim 5, characterized in that that the ratio Sr / Ba is equal to one in terms of measurement accuracy. Phosphor according to claim 1, characterized in that the strongest intensity XRD reflex of Phosphorus is a peak, with sufficient resolution a double peak, which is shifted to shorter angles towards the highest intensity XRD reflection of Sr-Sion at about 31.6 ° (2 Θ). Phosphor according to claim 1, characterized in that that in the X-ray diffraction pattern a group of three strong reflections occurs between 52 ° and 58 °. Light source with primary radiation coming from a phosphor according to one of the preceding claims wholly or partly in longer-wave Radiation is converted. Light source according to claim 9, characterized that the light source is an LED. Light source according to claim 9, characterized that the primary radiation has a peak at 440 to 465 nm. Light source according to claim 9, characterized that more phosphors are used together with the mixing sion be, especially another Sion. Process for the preparation of a mixed sion according to of the preceding claims, characterized in that carbonates of Sr and Ba together with SiO2 and a flux and an Eu precursor intense mixed and from which an orthosilicate is synthesized, this afterwards is mixed with Si3N4 and this mixture subsequently in slightly reducing atmosphere annealed becomes.